Grading machines (e.g., length grading machines), or grain separators, are typically used to separate a stream of grain containing various types and sizes of grain into its constituent parts, for example, wheat, durum, oats, barley and rice, and/or to separate such grains from seed contaminants. Examples of grading machines are discussed in U.S. Pat. Nos. 7,029,393 and 7,862,412, the contents of each of which are hereby incorporated by reference. These machines generally employ a rotating member, or cylinder, which is mounted in an interior space of a housing of the grain separator, and which includes lifting pockets, or indentations, located along an interior surface thereof. As the cylinder rotates, the indentations, according to their size, receive and lift particular lengths, or sizes, of granules out of a stream of grain and drop the granules into a trough that is mounted within the cylinder. The stream of grain is fed into the rotating cylinder by a spout, which extends through a sidewall of the housing and through an end piece of the indented cylinder.
To prevent grain from leaking out at an interface between the spout and the rotating cylinder, a fixed (i.e., non-rotating) seal is typically mounted about the spout so as to interface with an external surface of the cylinder end piece. Typically, these seals have been made from either relatively hard plastic or soft fibrous materials such as felt or sheep's skin. These seals rely on the contact surface area and/or the packing ability of the seal material to prevent granular material from moving past the seal. These typical materials are not conformal with the spout, and generally leave a small gap or clearance between the seal and the spout at least partially around the circumference of the seal/spout interface. Because of this clearance, it is common for both whole and broken grains to push their way past the seal, causing leakage and/or damage to the seal and sealing surface. Leakage of grain from the separating process is a nuisance and in many environments an unacceptable problem.